• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2006.05a
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• pp.898-901
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• 2006

In this paper, effect of ceramic processing was investigated on the magnetic properties of low loss Mn-Zn ferrite. High frequency characteristics, high saturated magnetic flux density and high magnetic permeability and low magnetism loss are required for the development of Mn-Zn ferrite, which is parts in the communication. therefore, in order to improve Mn-Zn ferrite with a high frequency , it is important to have a minimal change of particles and to control the eddy current loss caused by high resistance of the stratum of particles and to reduce the hysteresis loss by uniform change of detailed structure. In this paper, we added $V_2O_5\;and\;CaCo_3$ to Mn-Zn Ferrite to achieve a high efficiency, low loss core material. The compositions are MnO : ZnO : $Fe_2O_3$ = 21 : 10 : 69 mol%. They were sintered at $1250^{\circ}C$ for Three hours. Initial permeability was measured at 0.1MHz. At 50mT, Power loss was measured by temperature changing at 100kHz.

• Korean Journal of Materials Research
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• v.2 no.3
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• pp.220-227
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• 1992

Electrorheological(ER) fluid's storage shear modulus(G') and loss factor(${\eta}$) have been directly measured using small amplitude forced oscillating rheometer as a function of oscillating frequency, strain amplitude and applied electric field. Two types of experiment were performed , (a) frequency sweep and (b) amplitude sweep. Two kinds of sample were employed for this experiment ; cornstarch particles in corn oil and zeolite particles in silicone oil. The storage shear modulus was a strong function of driving frequency. Generally, the modulus increased with driving frequency. On the other hand, the loss factor was not well behaved as storage modulus, but as the driving frequency increases the loss factor slightly decreases was the trend of the material's characteristics. Also the modulus was a strong function of strain amplitude. Generally, modulus decreased with increasing strain, but loss factor increases slightly with increasing strain amplitude. For G', cornstarch in corn oil ER fluid has higher values than zeolite based fluid as we increased applied electric field. On the other hand, zeolite based fluid has higher values for ${\eta}$. There is a reasonable agreement between theoretical calculation and experiment.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2017.05a
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• pp.230-231
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• 2017

The addition of a limestone filler(LF) to fill into the voids between cement and aggregate particles can reduce the cementitious paste volume. This paper aim to evaluate the influence of LF contents on the hydration kinetics and compressive strength. Hydration kinetics were evaluate using heat of hydration, ignition loss and thermal analysis. The heat of hydration was measured using Isothermal Calorimetry. The degree of hydration was measured using ignition loss. Hydration product analysis was carried out by Thermal Gravimetric and Differential Thermal Analysis. The results show that the addition of LF reduces not only the initial setting time and heat of hydration peak, also degree of hydration and rate of strength development at early age increase with the addition of LF. It can be concluded the LF fills the pore between cement particles due to formation of carboaluminate, which may accelerate the setting of cement pastes.

• Journal of the Korean Society for Precision Engineering
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• v.24 no.5
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• pp.82-88
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• 2007

This work is to fabricate a precise optical fiber array using polymer composite for optical interconnection. Optical fiber array has to satisfy low optical loss requirement less than 0.4 dB according to temperature change. For this purpose, design criteria for an optical fiber array was derived. The coefficient of thermal expansion of silica particulate epoxy composites was affected by volume fraction of silica particles. And also, elastic modulus of silica particulate epoxy composites was affected by volume fraction of silica particles. To obtain the coefficients of thermal expansion below $10{\times}10E-6/^{\circ}C$ and elastic modulus more than 20 GPa , we chose the volume fraction more than 76%. Using silica particulate epoxy composites with the volume fraction 76%, 8-channel optical fiber array with dimensional tolerances below $1\;{\mu}m$ was manufactured by transfer molding technique using dies with the uniquely-designed core pin and precisely-machined zirconia ceramic V block. These optical fiber arrays showed optical loss variations within 0.4 dB under thermal cycling test and high temperature test.

• Fire Science and Engineering
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• v.31 no.4
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• pp.7-11
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• 2017

The use of special gas masks such as PAPR is strongly required for the safe and efficient work of fire-fighters in removing fire residue and rescue activity. Special gas masks commonly use canisters with carbon activated particles. This paper analyzed the pressure distribution, velocity distribution and pressure loss characteristics in canisters using CFD simulation, and showed pressure drops are affected by inlet air velocity, canister geometry and increase dramatically especially with the decrease of particle diameters and volume fractions.

• Applied Biological Chemistry
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• v.29 no.3
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• pp.311-317
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• 1986

This experiment was conducted to find out the minimum size of pores through that Zeolite particles moved vertically out with percolated solution in the sand column and to estimate whether they were lost through the pores in the field sandy soil. The results were as follows. 1. The amount of Zeolite loss through sand columns was increased in the order of the columns filled with $2{\sim}1>1{\sim}0.5>0.5>0.25mm$ sand particles. 2. The Zeolite particles lost through columns filled with $1{\sim}0.5$ and $0.5{\sim}0.25mm$ sand were clay fraction. 3. The pore sire that clay fraction of Zeolite mineral could migrate through was determined to be above $150{\mu}m$ and Jangchon subsoil was presumed to have possibility of Zeolite loss in consideration of its pore size distribution. 4. The suitable particle size of Zeolite for application in sandy soil was presumed to be above $2{\mu}m$.

• Asian Journal of Atmospheric Environment
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• v.3 no.1
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• pp.27-41
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• 2009

Internally mixed states of submicron particles during transport from the Asian continent to the Pacific Ocean were analyzed using a single-particle time-offlight mass spectrometer. The observation was conducted at Tsukuba in Japan in the spring of 2005 in order to investigate springtime transport of particles from the continent. The sum of ion intensities of sulfate (${HSO_4}^-$) detected in particles originating from the continental air masses counted for 75% of that in all particles during the observation. By analyzing correlations among compounds, origins and internally mixed states of compounds were estimated. It was found that nitrate was mixed with sulfate-rich particles as the air mass approached Japan. It was confirmed that Asian mineral dust particles played significant roles for transport of continental sulfate to Japan. As a result of analysis on internal mixing of chlorine and nitrate, it was implied that the chlorine loss in fine sea salt particles had already proceeded at Tsukuba. It was characteristic that fluoride ions were significantly detected, coal combustion in the Asian Continent can be an important source of fluorides detected in Japan through the westward transportation of fine particles including fluorides.

• Journal of The Korean Society of Agricultural Engineers
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• v.56 no.6
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• pp.1-9
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• 2014

In this study the pore water pressures were measured in sea dike constructed with the sand dredged in the sea, and they were analyzed with the hydraulic head loss rate to estimate quantitatively the state of blocking seepage in the sea dike embankment. Blocking state was expressed as the number between 0 and 1. the number of 1 means the state of perfectly blocking seepage and the number of 0 means the state of sea water being passing free. The deeper the installed position was the lower the hydraulic head loss rate was and the longer the seepage path length was the higher the hydraulic head loss rate was. The estimated R-squareds were close to 1, which means that the embankment was steady state without movement of soil particles.

• The Journal of Korean Academy of Prosthodontics
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• v.27 no.1
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• pp.181-192
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• 1989

Loss of teeth causes the inevitable reduction of residual ridge. Among the various methods solving this problem, hydroxyapatite proved to be useful for correction of ridge defect and irregularity. The purpose of this study is to evaluate the tissue responses of two types Of hydroxyapatites and resin polymer. Calcitite 2040 (Calcitek Inc.), Interpore 200 (Interpore Int.), and HTR polymer (HTR Sciences) were implanted into the jaw of an adult dog. The procedure was designed to obtain the results of 1 week, 2 week, 4 week, and 12 week-intervals. And after 12 weeks from the first operation day, the dog was sacrificed and evaluated histologically by light microscope. The results were as follows : 1. The mucosa was healed after two weeks. 2. After 1 week, there were acute inflammatory cells, but diminished after 2 weeks and were not seen after 12 weeks. 3. The hydroxyapatites implanted in soft tissues were surrounded by fibrous connective tissue. And some foreign body giant cells were found. 4. Calcitite and Interpore particles implanted subperiosteally were surrounded by newly formed bone after 12 months. And direct contact between bone and particles was noted. 5. The HTR particles implanted in soft tissues were encapsulated by fibrous connective tissues. The sample where the particles contacted directly to bone could not obtained by some probable insufficiencies of surgical technique or care of the animal. And the residue of HTR particles was digested by macrophage.

• Particle and aerosol research
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• v.7 no.4
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• pp.123-130
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• 2011

Previous designs of conventional aerodynamic lenses have a limitation of narrow range of focusable particle size, e.g. 30 to 300nm or 3 to 30nm. To enlarge the focusable size range to 30-3000nm, it is necessary to avoid a significant loss of particles larger than 300nm inside the lenses. From numerical simulations on size-resolved particle trajectories, we confirmed that the traveling losses of such large particles could be avoided only when the radial position of particles approaching the orifice lens was near the lens axis. Hence, we designed the lens system consisting of a converging-diverging nozzle and 7 orifices to fulfill the requirement. In particular, the orifices were aligned in a way that their diameters were descending and ascending to the downstream. As a result, 30-2800nm particles can be focused to the particle beam of 0.2mm or less in radius with above 85% transmission efficiency. Even $10{\mu}m$ particles can be focused with 74% of transmission efficiency.